Antenna compensation system and method in a communications device

ABSTRACT

A communications device is provided. The communications device includes an antenna port, transmitter circuitry configured to broadcast a radio frequency (RF) output signal across the antenna port, and a controller configured to adjust a signal level of the RF output signal in accordance with antenna compensation information. The antenna port, the transmitter circuitry, and the controller are at least partially integrated on the same integrated circuit.

BACKGROUND

Radio frequency (RF) transmitters are used in a wide variety ofapplications such as cellular or mobile telephones, cordless telephones,personal digital assistants (PDAs), computers, radios and other devicesthat transmit RF signals. As transmitters become increasingly integratedand more portable, the efficiency in generating and transmitting anoutput signal of the transmitter tends to increase in importance. Forexample, a transmitter may seek to minimize the amount of power it usesto generate and transmit a signal to prolong the operation of a portablepower source such as a battery.

Electrical circuit properties of a transmitter and an antenna connectedto the transmitter affect the operation of the transmitter. Theseproperties may cause a transmitter to operate with increased ordecreased efficiency, depending on the properties of the transmitter andthe antenna. Although manufacturers of transmitters and antennatypically provide typical electrical circuit properties of thesecomponents, these properties may vary slightly from component tocomponent and result in an operation of the components that is less thanoptimal in some configurations. In addition, system designers may have aneed for flexibility of the electrical circuit properties of a componentto meet design criteria of a larger system.

SUMMARY

According to one exemplary embodiment, a communications device isprovided. The communications device includes an antenna port,transmitter circuitry configured to broadcast a radio frequency (RF)output signal across the antenna port, and a controller configured toadjust a signal level of the RF output signal in accordance with antennacompensation information. The antenna port, the transmitter circuitry,and the controller are at least partially integrated on the sameintegrated circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one embodiment of acommunications device.

FIG. 2 is a schematic diagram illustrating one embodiment of atransmitter model in a communications device.

FIGS. 3A-3D are schematic diagrams illustrating embodiments of antennasand antenna circuit models.

FIG. 4 is a block diagram illustrating one embodiment of selectedportions of transmitter circuitry.

FIG. 5 is a schematic diagram illustrating one embodiment of outputstage circuitry with adjustable output level circuitry.

FIG. 6 is a graphical diagram illustrating one embodiment of an LCfilter response.

FIG. 7A is a schematic diagram illustrating one embodiment of tuningcircuitry.

FIG. 7B is a schematic diagram illustrating another embodiment of tuningcircuitry.

FIG. 8 is a flow chart illustrating one embodiment of a method forcalibrating a communications device.

FIG. 9 is a table illustrating one embodiment of information for use incompensating for parameters of an antenna.

FIG. 10 is a block diagram illustrating another embodiment of acommunications device.

FIG. 11 is a block diagram illustrating one embodiment of a portablecommunications system that includes a communications device.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

As described herein, an integrated low power communications device isprovided for use in transmitting radio-frequency (RF) signals or signalsfrom other frequency bands. According to one or more embodiments, thecommunications device includes dual antenna ports, tuning circuitryconnected to at least one of the antenna ports, adjustable levelcircuitry for the input and output signals to and from the output stageof the transmitter, and calibration circuitry. The dual antenna portsallow the communications device to be optimized for various types ofantenna. The tuning circuitry, adjustable level circuitry, andcalibration circuitry provide the ability to filter, adjust andcalibrate the output of the transmitter for various frequencies andsignal levels. The adjustable level circuitry also allows thecommunications device to compensate for antenna properties over a rangeof frequencies. The dual antenna ports, tuning circuitry, adjustablelevel circuitry, and calibration circuitry may be at least partiallyintegrated on-chip, i.e., at least partially integrated the sameintegrated circuit, according to one or more embodiments.

The on-chip dual antenna ports, tuning circuitry, adjustable levelcircuitry, and calibration circuitry described herein may be used withrespect to a wide variety of integrated communications systems. The lowpower radio-frequency (RF) integrated transmitter and transceiverembodiments described below with reference to FIGS. 1 and 10,respectively, represent integrated communications devices that can takeadvantage of the dual antenna ports, tuning circuitry, adjustable levelcircuitry, and calibration circuitry described herein. Althoughterrestrial RF broadcast transmitters, e.g., FM and AM transmitters, aredescribed herein, these transmitters are presented by way of example. Inother embodiments, other broadcast bands may be used.

The architectures of the communications devices described herein mayadvantageously provide flexibility in selecting an antenna for use withthe devices while allowing efficient operation of the devices. Inaddition, architectures may advantageously increase the quality of atransmitted signal by providing optimal filtering and tuning of thesignal. The architectures may also advantageously optimize powerconsumption by adjusting a signal level of the output signal to anoptimum level. Further, the architectures may advantageously provide forthe shared use of components in a device with both a transmitter and areceiver.

FIG. 1 is a block diagram illustrating a communications device 10 thatforms an integrated terrestrial RF broadcast transmitter according toone embodiment. Communications device 10 includes a transmittercircuitry 100 and a controller 102. Transmitter circuitry 100 includesdriver circuitry 104 and output stage circuitry 106. Controller 102controls the operation and signal levels of driver circuitry 104 usinginput level control and output stage circuitry 106 using output levelcontrol signals.

Driver circuitry 104 receives an input voltage signal, V_(IN). The inputvoltage signal may be received by driver circuitry 104 in any suitableanalog or digital form. Driver circuitry 104 generates a radio frequency(RF) voltage signal, V_(RF), using the input voltage signal and providesthe RF voltage signal to output stage circuitry 106. Output stagecircuitry 106 receives the RF voltage signal, generates a first RFoutput voltage signal, V_(OUT1), and RF output current, I_(OUT), andprovides the first RF output voltage signal and the RF output current ona signal line 107 to output stage circuitry 108 and a first antenna port110. Output stage circuitry 108 receives the first RF output voltagesignal, generates a second RF output voltage signal, V_(OUT2), andprovides the second RF output voltage signal on a signal line 109 to asecond antenna port 112.

Antenna ports 110 and 112 are configured to be connected to separateantennas. Each antenna port 110 and 112 forms an output pad inintegrated communications device 10 that includes a conductor configuredto couple to an antenna or other circuitry that is external tocommunications device 10. The output pads may be coupled toelectrostatic discharge (ESD) protection circuitry (not shown) or otheroutput buffer circuitry (not shown) in communications device 10. In theembodiment shown in FIG. 1, an antenna 130 and an inductor 132 connectto antenna port 110. In other embodiments, antenna 130 and inductor 132may be omitted and another antenna (not shown) may connect to antennaport 112. In further embodiments, inductor 132 may omitted, locatedintegrated on-chip with communications device 10, or represent theinductance of antenna 130. In some embodiments, output stage circuitry108 and antenna port 112 may not be used.

Tuning circuitry 114 and inductor 132 are coupled in parallel betweensignal line 107 and ground (or other suitable potential) to connect toantenna port 110, the output of transmitter circuitry 100, and the inputof output stage circuitry 108. Tuning circuitry 114 and inductor 132combine to form LC filter circuitry 140. Controller 102 provides controlsignals to tuning circuitry 114 to adjust the amount of capacitanceand/or resistance of that tuning circuitry 114 provides on antenna port110 to adjust the filter response of LC filter circuitry 140. Byadjusting the amount of capacitance and/or resistance of tuningcircuitry 114, controller 102 also affects the signal response onantenna port 112.

Level detect circuitry 116 connects to the output of driver circuitry104 across a switch 118A and to the output of output stage circuitry 106across a switch 118B. Controller 102 provides control signals to eachswitch 118A and 118B to selectively connect the output of drivercircuitry 104 and/or the output of output stage circuitry 106 to leveldetect circuitry 116. When connected to the output of driver circuitry104, level detect circuitry 116 detects the RF voltage signal, V_(RF),and provides one or more signal level measurements of the RF voltagesignal to controller 102. When connected to the output of output stagecircuitry 106, level detect circuitry 116 detects the first RF outputvoltage signal, V_(OUT1), and provides one or more signal levelmeasurements, i.e. amplitudes, of the first output voltage signal tocontroller 102. In other embodiments, switch 118A and/or switch 118B maybe omitted or replaced with equivalent circuitry. In addition,additional switches or other circuitry (not shown) may be included toallow level detect circuitry 116 to detect the second RF output voltagesignal, V_(OUT2), and provide one or more signal level measurements,i.e. amplitudes, of the second output voltage signal to controller 102.

Controller 102 includes a connection 150 that is configured to allow auser 152 to provide information to and receive information fromcontroller 102. The information provided by user 152 to controller 102may be used to select the output signal frequency generated bytransmitter circuitry 100 and may include antenna compensationinformation as described in additional detail below.

As illustrated by a line 120 in FIG. 1, transmitter circuitry 100,controller 102, output stage circuitry 108, tuning circuitry 114, leveldetect circuitry 116, and switches 118A and 118B are located on-chip andare at least partially integrated on the same integrated circuit (i.e.,on a single chip that is formed on a common substrate) according to oneembodiment. Antenna 130 and inductor 132 are located off-chip (i.e.,external to the common substrate that includes communications device10).

As used herein, an RF signal means an electrical signal conveying usefulinformation and having a frequency from about 3 kilohertz (kHz) tothousands of gigahertz (GHz), regardless of the medium through which thesignal is conveyed. Thus, an RF signal may be transmitted through air,free space, coaxial cable, and/or fiber optic cable, for example.

For purposes of illustration, the output signals of communicationsdevice 10 described herein may be transmitted in signal bands such as AMaudio broadcast bands, FM audio broadcast bands, television audiobroadcast bands, weather channel bands, or other desired broadcastbands. The following table provides example frequencies and uses forvarious broadcast bands that may be transmitted by communications device10.

TABLE 1 EXAMPLE FREQUENCY BANDS AND USES FREQUENCY USES/SERVICES 150-535kHz European LW radio broadcast 9 kHz spacing 535-1700 kHz MW/AM radiobroadcast U.S. uses 10 kHz spacing Europe uses 9 kHz spacing 1.7-30 MHzSW/HF international radio broadcasting 46-49 MHz Cordless phones, babymonitors, remote control 59.75 (2) MHz U.S. television channels 2-6(VHF_L) 65.75 (3) MHz 6 MHz channels at 54, 60, 66, 76, 82 71.75 (4) MHzAudio carrier is at 5.75 MHz (FM MTS) 81.75 (5) MHz 87.75 (6) MHz 47-54(E2) MHz European television 54-61 (E3) MHz 7 MHz channels, FM sound61-68 (E4) MHz Band I: E2-E4 174-181 (E5) MHz Band II: E5-E12 181-188(E6) MHz 188-195 (E7) MHz 195-202 (E8) MHz 202-209 (E9) MHz 209-216(E10) MHz 216-223 (E11) MHz 223-230 (E12) MHz 76-91 MHz Japan FMbroadcast band 87.9-108 MHz U.S./Europe FM broadcast band 200 kHzspacing (U.S.) 100 kHz spacing (Europe) 162.550 (WX1) MHz U.S. WeatherBand 162.400 (WX2) MHz 7 channels, 25 kHz spacing 162.475 (WX3) MHzSAME: Specific Area Message Encoding 162.425 (WX4) MHz 162.450 (WX5) MHz162.500 (WX6) MHz 162.525 (WX7) MHz 179.75 (7) MHz U.S. televisionchannels 7-13 (VHF_High) 6 MHz channels at 174, 180, 186, 192, 198, 204,210 215.75 (13) MHz FM Sound at 5.75 MHz 182.5 (F5) MHz Frenchtelevision F5-F10 Band III 8 MHz channels 224.5 (F10) MHz Vision at 176,184, 192, 200, 208, 216 MHz AM sound at +6.5 MHz 470-478 (21) MHz BandIV - television broadcasting Band V - television broadcasting 854-862(69) MHz 6 MHz channels from 470 to 862 MHz U.K. System I (PAL): Offsetsof +/−25 kHz may be used to alleviate co-channel interference AM Visioncarrier at +1.25 (Lower Sideband vestigial) FMW Sound carrier at +7.25Nicam digital sound at +7.802 French System L (Secam): Offsets of+/−37.5 kHz may be used AM Vision carrier at +1.25 (inverted video) FMWSound carrier at +7.75 Nicam digital sound at +7.55 470-476 (14) MHzU.S. television channels 14-69 6 MHz channels 819-825 (69) MHz Soundcarrier is at 5.75 MHz (FM MTS) 14-20 shared with law enforcement

Antenna ports 110 and 112 allow various antennas to be connected to andoperate with communications device 10. Antenna port 110 connects tooutput stage circuitry 106. As will be described below with reference tothe embodiment of FIG. 5, output stage circuitry 106 may include a highimpedance amplifier, such as a transconductance amplifier 502 (FIG. 5),and high impedance output stage circuitry, such as adjustable levelcircuitry 504 (FIG. 5), to provide a high impedance on antenna port 110.Antenna port 112 connects to output stage circuitry 108 to provide animpedance on antenna port 112 that differs from the impedance on antennaport 110. For example, the impedance on antenna port 112 may be higheror lower than the impedance on antenna port 110.

FIG. 2 is a schematic diagram illustrating one embodiment of a model oftransmitter circuitry 100 in RF applications and specifically, in aportable low power embodiment of transmitter circuitry 100 operating atmoderate frequencies such as the FM broadcast band. The input signal isamplified with a gain of A to produce the first RF output voltage signalon antenna port 110. The amplifier presents an impedance to antenna 130of Z_(OUT), and antenna 130 presents an impedance to the amplifier ofZ_(ANT).

The amplifier impedance may be chosen to match the antenna impedance, oran impedance matching network may be inserted between the amplifieroutput and the antenna to match amplifier impedance and the antennaimpedance. By matching the impedances, reflections between the amplifierand the antenna port may be reduced or eliminated.

FIGS. 3A-3D are schematic diagrams illustrating antenna embodiments 302,312, 322, and 332, respectively, and corresponding antenna circuitmodels 304, 314, 324, and 334, respectively. Antennas 302, 312, 322, and332 may each be used with communications device 10 by coupling one ofantennas 302, 312, 322, or 332 to one of antenna ports 110 or 112.

FIG. 3A illustrates a quarter-wave antenna 302 perpendicular to a groundplane with a length, L, defined by a wavelength, λ=c/f where c is thespeed of light and f is the RF frequency. Impedance model 304 includes aloss resistance, R_(L), a series reactance, X_(a), and a radiationresistance, R_(r), in series. For an ideal quarter-wave antenna 302, theloss resistance, R_(L), and series reactance, X_(a), will be zero. Theantenna impedance is approximately 37 ohms due to the radiationresistance, R_(r). The radiation resistance is the equivalent circuitelement that converts the dissipated power into radiated power. Manyfactors may cause the actual impedance to differ significantly from thisvalue. If the RF frequency and required length do not exactly match, theimpedance may be greater due to non-zero values for the seriesreactance. The series reactance may be capacitive if the length isshorter than the ideal length and inductive if the length is longer thanthe ideal length. If the ground plane is not ideal, the impedance mayalso differ due to added impedance in the series reactance or the lossresistance or both. If antenna 302 is near other objects, the impedancemay differ from that of the ideal antenna.

FIG. 3B illustrates a short monopole antenna 312 with a length, L, thatis much smaller than a wavelength, λ, as defined above. Impedance model314 includes a capacitance, C_(a), in series with a radiationresistance, R_(r). For an embodiment of antenna 312 of severalcentimeters at frequencies of 100 MHz, the capacitance may be on theorder of 1 pF and the radiation resistance may be on the order of 1 ohm.At this frequency, the total impedance is largely reactive and on theorder of 1 kilo-ohm.

FIG. 3C illustrates a loop antenna 322 that is driven single-ended withthe other end at a reference potential. Loop antenna 322 may be chosento be a small loop with a circumference that is small compared to thewavelength, λ, as defined above, in one or more embodiments. Impedancemodel 324 includes a resonating capacitance, C_(p), in parallel with aloss resistance, R_(L), a radiation resistance, R_(r), and aninductance, L_(L), connected in series. The inductance is calculatedfrom the geometry of loop antenna 322. For an embodiment of loop antenna322 of a few centimeters in diameter, the inductance may be on the orderof 100 nH. The loss resistance depends on the resistive properties ofthe conductor used and may be on the order of 0.1 ohm. The radiationresistance may also be very small and may be on the order of 0.01 ohm.When resonated with the resonating capacitance, the network may be of avery high Q, where Q is the ratio of the center frequency of the networkto the bandwidth of the network. At the resonant frequency, an impedancemodel 326 represents the equivalent circuit with the reactance of thecapacitor and the inductor canceling each another and the equivalentresistances are multiplied by Q². Accordingly, loop antenna 322 atresonance may present a very high impedance that may be on the order ofseveral kilo-ohms and may have significant radiation resistance.

FIG. 3D illustrates a random wire antenna 332 with a length, L, that canvary as smaller or larger than a wavelength, λ, as defined above. Randomwire antenna 332 may be implemented by coupling the output fromtransmitter circuitry 100 to a conductor. The conductor may also serveas a power cord (not shown) or a headphone wire (shown in FIG. 3D), forexample. Random wire antenna 332 may approximate quarter-wave antenna302 as described above with reference to FIG. 3A. Accordingly, theimpedance of random wire antenna 332 may vary greatly due to non-ideallength, improper ground plane, and proximity to other objects.

Antennas 302, 312, 322, and 332 illustrate that a transmitter circuitry100 with an exact driving impedance to match a transmission line orideal antenna (e.g., a 50 or 75 ohm antenna) may not be a perfect matchfor many situations. The architecture of communications device 10, asdescribed herein, may advantageously optimize the circuit for drivingboth high and low impedance antennas.

FIG. 4 is a block diagram illustrating an embodiment 104A of drivercircuitry 104. In embodiment 104A, the input voltage signal, V_(IN),includes left (L) and right (R) analog audio input channels that arereceived by analog-to-digital converters (ADC) 402 and 404,respectively. ADCs 402 and 404 convert the analog audio input channelsto first and second sets N bit digital signals, respectively, andprovide the sets of N bit digital signals to processing circuitry 406.

Processing circuitry 406 receives the sets of N bit digital signals fromADCs 402 and 404, respectively. Processing circuitry 406 performs anysuitable audio processing on the signal sets such as signal conditioning(e.g., tone, amplitude, or compression) and stereo encoding for FMbroadcast. Processing circuitry 406 provides the processed signals todigital intermediate frequency (IF) generation circuitry 408.

Digital IF generation circuitry 408 receives the processed signals fromprocessing circuitry 406. Digital IF generation circuitry 408 upconvertsthe processed signals to an intermediate frequency and provides theupconverted signals to digital-to-analog converters (DAC) 410 and 412.In the embodiment of FIG. 4, digital IF generation circuitry 408upconverts the processed signals to produce a quadrature output withreal (I) and imaginary (Q) signals. Digital IF generation circuitry 408provides the real signals to DAC 410 and the imaginary signals to DAC412. In other embodiments, digital IF generation circuitry 408upconverts the processed signals to produce other signal types.

DACs 410 and 412 receive the upconverted signals from digital IFgeneration circuitry 408 and convert the digital upconverted signals toanalog signals. DACs 410 and 412 provide the analog signals to RF mixer414.

RF mixer 414 receives the analog signals from DACs 410 and 412. RF mixer414 upconverts the analog signals to a desired output (transmit)frequency by combining the analog signals with phase shifted localoscillator (LO) mixing signals provided by local oscillator (LO)generation circuitry 416. LO generation circuitry 416 includesoscillation circuitry (not shown) and outputs the two out-of-phase LOmixing signals that are used by RF mixer 414. RF mixer 414 also combinesthe real and imaginary signals such that the RF signal forms a real RFsignal. RF mixer 414 provides the RF signal to RF conditioning circuitry418.

RF conditioning circuitry 418 receives the RF signal from RF mixer 414.RF conditioning circuitry 418 filters the RF signal to remove undesiredsignals and adjusts a signal level, i.e. amplitude, of the RF signal toa desired level in response to an input level control signal 420 fromcontroller 102. RF conditioning circuitry 418 provides the adjusted RFvoltage signal, V_(RF), to output stage circuitry 106 (FIG. 1). Insetting the signal level of the RF signal, controller 102 activatesswitch 118A to couple level detect circuitry 116 to the RF voltagesignal. Level detect circuitry 116 detects the signal level of the RFvoltage signal and provides any suitable inputs to controller 102 toidentify the signal level of the RF voltage signal to controller 102.Controller 102 may iteratively adjust the signal level and receivefeedback from level detect circuitry 116 until a desired signal level isachieved. Controller 102 may adjust the signal level to achieve anoptimum level of the RF voltage signal for efficient drive into outputstage circuitry 106.

RF conditioning circuitry 418 may adjust the signal level of the RFvoltage signal in any suitable way. For example, RF conditioningcircuitry 418 may include a variable attenuator or a programmable gainamplifier. Further, portions of driver circuitry 104A other than or inaddition to RF conditioning circuitry 418 may be configured to adjustthe signal level of the RF voltage signal, V_(RF), in response to inputlevel control signals from controller 102. For example, one or more ofdigital IF generation circuitry 408, DACs 410 and 412, and RF mixer 414may be configured to adjust the signal level of the RF voltage signal,V_(RF), in other embodiments allowing the gain or gains of digital IFgeneration circuitry 408, DACs 410 and 412, and/or RF mixer 414 to beadjusted by controller 102.

In other embodiments, driver circuitry 104 may include any othersuitable types and arrangements of circuitry configured to generate anRF voltage signal. For example, digital IF generation circuitry 408 maybe omitted in other embodiments.

Referring back to FIG. 1, communications device 10 is configured todrive the impedances that may be encountered with varying antenna typesusing output stage circuitries 106 and 108, antenna ports 110 and 112,and tuning circuitry 114.

Output stage circuitry 106 generates the first RF output signal,V_(OUT1), in response to receiving an RF input signal, V_(RF), fromdriver circuitry 104 and provides the first RF output signal to antennaport 110 and output stage circuitry 108. Antenna port 110 receives thefirst RF output signal from output stage circuitry 106 and provides theRF output signal to antenna 130. Controller 102 provides control signalsto output stage circuitry 106 to adjust the output signal level, i.e.amplitude, generated by output stage circuitry 106. Output stagecircuitry 106 is configured to present a high impedance to antenna port110 and antenna 130.

In one embodiment, output stage circuitry 106 includes an amplifyingstage with a high impedance output that produces the RF output current,I_(OUT). The RF output signal voltage on signal line 107 is determinedfrom the RF output current produced by the amplifying stage and thetotal load impedance, Z_(LOAD), of antenna 130 as shown in Equation I.V _(OUT1) =I _(OUT) *Z _(LOAD)  EQUATION IIn this embodiment, controller 102 provides control signals to outputstage circuitry 106 to adjust the amount of output current generated byoutput stage circuitry 106. By adjusting the output current, controller102 adjusts the output signal voltage level on signal line 107. For highimpedance antennas coupled to antenna port 110, (e.g., in embodimentswhere antenna 130 is short monopole antenna 312 or resonated loopantenna 322), output stage circuitry 106 provides a power efficient wayto produce a voltage on antenna 130.

FIG. 5 is a schematic diagram illustrating an embodiment 106A of outputstage circuitry 106 with a transconductance amplifier 502 and adjustableoutput level circuitry 504. Transconductance amplifier 502 is a highimpedance amplifier that generates a signal current, I_(S), inproportion to the voltage of RF input signal, V_(RF). Adjustable outputlevel circuitry 504 includes transistors M₀ through M_(n) and switches506(1) through 506 (n), where n is an integer greater than or equal totwo.

Transistors M₀ and M₁ form a current mirror, with the output currentfrom transistor M₁ being related to the current in M₀ by a ratio of n1.Similarly, the current in M₂ is proportional to the current in M₀ by aratio of n2, and the current in M_(n) is proportional to the current inM₀ by a ratio of n(n).

Switches 506(1) through 506 (n) are in series with the output current oftransistors M₁ through M_(n), respectively. Controller 502 providescontrol signals S₁ through S_(n) to switches 506(1) through 506 (n),respectively, to turn on or off the output current from each transistorM₁ through M_(n) on signal line 107. The sum of the currents on signalline 107 forms the RF output current I_(OUT). Control signals S₁ throughS_(n) collectively form the output level control signals shown in FIG.1.

Controller 102 controls the output voltage provided to antenna port 110by adjusting the output signal current. The power dissipated by outputstage circuitry 106A may only need to be sufficient to produce a desiredsignal current and resulting output voltage on signal line 107.

Referring back to FIG. 1, output stage circuitry 106 may also be used todrive a low impedance load (e.g., a 50 ohm load) such as quarter-waveantenna 302 or test equipment. Because of the low impedance load, theoutput voltage on signal line 107 may not need to be as large for agiven output current. The reduced voltages may allow quarter-waveantenna 302 or test equipment to operate with acceptable performance forthe application. Output stage circuitry 106 is therefore a powerefficient way of generating a small signal for these applications.

A low impedance load may reduce the Q of LC filter circuitry 140 andthereby reduce the effectiveness of LC filter circuitry 140 in filteringundesired RF signals. If a communications system does not requireadditional filtering of undesired RF signals, then antenna port 110 mayprovide a power efficient circuit for driving a low impedance load atmodest signal levels.

If additional filtering is desired, then output stage circuitry 108 andantenna port 112 may be used for low impedance loads, such asquarter-wave antenna 302 or test equipment, or other loads that have animpedance that differs from the impedance presented on antenna port 110.Output stage circuitry 108 generates the second RF output signal,V_(OUT2), in response to receiving the first RF output signal, V_(OUT1),from output stage circuitry 106 and provides the second RF output signalto antenna port 112. Antenna port 112 receives the second RF outputsignal from output stage circuitry 108 and provides the RF output signalto a coupled antenna (not shown).

In one embodiment, output stage circuitry 108 includes an amplifier (notshown) with an impedance that differs from the impedance of output stagecircuitry 106 and, more particularly, from adjustable level circuitry504 in output stage circuitry 106A. The impedance of the amplifier ofoutput stage circuitry 108 may be selected to match the impedance of aload or be higher or lower than the impedance of a load. The amplifiermay be turned off by controller 102 to save power when it is not used.Output stage circuitry 108 is configured to present an impedance toantenna port 112 and an antenna coupled to antenna port 112 (not shown)that differs from the impedance presented by output stage circuitry 106to antenna port 110 and antenna 130.

In other embodiments, output stage circuitry 108 includes adjustablelevel circuitry (not shown) configured to allow controller 102 to adjustthe signal level of the second RF output signal, V_(OUT2), on signalline 109. In these embodiments, the adjustable level circuitry may havean impedance that differs from the impedance of output stage circuitry106 and, more particularly, from adjustable level circuitry 504 inoutput stage circuitry 106A.

As noted above, tuning circuitry 114 and inductor 132 combine to form LCfilter circuitry 140. With some antennas, such as loop antenna 322 (FIG.3C), inductor 132 may be the inductance of the antenna rather than aseparate inductor. Controller 102 provides control signals to tuningcircuitry 114 to adjust the amount of capacitance and/or resistance ofthat tuning circuitry 114 provides on antenna port 110 to adjust the LCfilter response of LC filter circuitry 140. By adjusting the amount ofcapacitance and/or resistance of tuning circuitry 114, controller 102also affects the signal response on antenna port 112.

FIG. 6 is a graphical diagram illustrating one embodiment of an LCfilter response 600 of LC filter circuitry 140 with respect to a signal602 on signal line 107. Filter response 600 has a center frequency off_(LC) that is indicated by a dotted line 604 and a tuning range 610that varies from a low frequency f_(L) to a high frequency f_(H). Signal602 has a frequency of f_(CAL). By adjusting the tuning of tuningcircuitry 114, controller 102 moves LC filter response 600 up or downwithin the tuning range 610 for LC filter circuitry 140 as indicated byarrows 606 and 608, respectively. Signal 602 strengthens as controller102 aligns it closer to center frequency 604 for LC filter response 600.Accordingly, controller 102 may improve and/or optimize the strength ofsignal 602 on signal line 107 in the process of tuning LC filtercircuitry 140 for a desired channel or frequency of signal 602.

In the process of tuning signal 602, controller 102 activates switch118B to couple level detect circuitry 116 to the first RF output signal,V_(OUT1), on signal line 107. Level detect circuitry 116 detects thesignal level of the first RF output signal and provides any suitableinputs to controller 102 to identify the signal level of the first RFoutput signal to controller 102. Controller 102 may iteratively adjustthe tuning of tunable circuitry 114 and receive feedback from leveldetect circuitry 116 until a desired tuning is achieved.

To tune tuning circuitry 114, controller 102 provides control signals toselect a capacitance and/or a resistance of tuning circuitry 114. FIG.7A is a schematic diagram illustrating an embodiment 114A of tuningcircuitry 114. Tuning circuitry 114A includes a variable capacitor 702and a variable resistor 704 coupled in parallel between signal line 107and ground. Controller 102 provides control signals 706 to adjustvariable capacitor 702 and variable resistor 704 to adjust the tuning oftuning circuitry 114A. Variable capacitor 702 may be any suitablecircuitry configured to allow the capacitance of the circuitry to beadjusted by controller 102, and variable resistor 704 may be anysuitable circuitry configured to allow the resistance of the circuitryto be adjusted by controller 102.

FIG. 7B is a schematic diagram illustrating another embodiment 114B oftuning circuitry 114. Tuning circuitry 114B includes a set of cells710(1) through 710(m), where m is an integer greater than or equal toone, and referred to herein individually as a cell 710 or collectivelyas cells 710. Each cell 710 include a capacitive element 712, a pair oftransistors 714 and 716, and a resistive element 718 that are inparallel. Each capacitive element 712 couples between signal line 107 onone end and transistor 714 and resistive element 718 on the other end.Each transistor 714 forms a switch between capacitive element 712 andground that is controlled by a respective one of a set of signals 720from controller 102, where the set of signals 720 includes signals720(1) through 720(m). Each transistor 716 forms a switch betweenresistive element 718 and ground that is controlled by a respective oneof a set of signals 722 from controller 102, where the set of signals722 includes signals 722(1) through 722(m).

Capacitive elements 712 may each have the same or different nominalcapacitances. For example, a first group of ten cells 710 may havecapacitive elements 712 with nominal capacitances of 4 pF, a secondgroup of seven cells 710 may have capacitive elements 712 with nominalcapacitances of 1 pF, and a third group of seven cells 710 may havecapacitive elements 712 with nominal capacitances of 0.25 pF accordingto one embodiment.

In a normal mode of operation, controller 102 selectively activatesswitches 714 to select the amount of capacitance of tuning circuitry114B. By activating switch 714 in a given cell 710, controller 102causes a capacitive element 712 to be coupled between signal line 107and ground in the given cell 710. Controller 102 causes a capacitiveelement 712 to float (i.e., not be coupled between signal line 107 andground) by de-activating a switch 714 in a given cell 710. To increasethe capacitance of tuning circuitry 114B, controller 102 may increasethe number of capacitive elements 712 coupled between signal line 107and ground using signals 720. Likewise, controller 102 may increase thenumber of floating capacitive elements 712 to decrease the capacitanceof tuning circuitry 114B.

In a low Q mode of operation, controller 102 selectively activatesswitches 716 to select the amount of capacitance and the amount ofresistance of tuning circuitry 114B. By increasing the amount ofresistance of tuning circuitry 114B, controller 102 lowers the overall Qof LC filter circuitry 140 in the low Q mode of operation.

Because output stage 106 has a high impedance, antenna port 110 forms ahigh impedance node and LC filter circuitry 140 forms a high Q filter.The Q of LC filter circuitry 140 is determined by the ratio of totalequivalent parallel resistance to the reactance of either inductor 132or the capacitance of tuning circuitry 114 (i.e., the inductor 132 orthe capacitance of tuning circuitry 114 have the same value atresonance). In addition, the Q of LC filter circuitry 140 is the ratioof the center frequency of the filter to the bandwidth of the filter.Because of the high Q, LC filter response 600 of LC filter circuitry 140may be narrow and may reduce undesirable signals, such as signalharmonics, generated by components of transmitter circuitry 100. Thehigh Q, however, may increase the difficulty of tuning LC filtercircuitry 140.

To decrease the effective Q of tuning LC filter circuitry 140,controller 102 adjusts the amount of resistance of tuning circuitry 114Bby selectively activating switches 716 to couple selected resistiveelements 718 to ground. In this way, controller 102 is configured toadjust the resistance of tuning circuitry 114B.

By activating switch 716 in a given cell 710, controller 102 causes acapacitive element 712 and a resistive element 718 to be coupled inseries between signal line 107 and ground in the given cell 710.Controller 102 causes a capacitive element 712 to float (i.e., not becoupled between signal line 107 and resistive element 718) byde-activating a switch 716 in a given cell 710. To increase thecapacitance and the resistance of tuning circuitry 114B, controller 102may increase the number of capacitive elements 712 and resistiveelements 718 that are coupled in series between signal line 107 andground using signals 720. Likewise, controller 102 may decrease thenumber of capacitive elements 712 and resistive elements 718 that arecoupled in series between signal line 107 and ground using signals 720to decrease the capacitance and the resistance of tuning circuitry 114B.

FIGS. 7A and 7B illustrate example embodiments 114A and 114B of tuningcircuitry 114. In other embodiments of tuning circuitry 114, othercapacitive elements or inductive elements may be used, and the otherelements may be located on-chip or off-chip of communications device 10.In addition, other types and/or numbers of control signals may beprovided from controller 102 or an off-chip controller (not shown) toadjust any of the embodiments of tuning circuitry 114. Further, otherarrangements of resistive elements may be used to allow the resistanceof tuning circuitry 114 to be adjusted in other ways.

Referring back to FIG. 1, communications device 10 is configured tooperate in a calibration mode of operation. During the calibration modeof operation, controller 102 adjusts the signal level of the RF voltagesignal, V_(RF), adjusts the signal level of the first RF output voltagesignal, V_(OUT1), and tunes LC filter circuitry 140 to optimize theoperation of communications device 10. Controller 102 may perform thesefunctions in any suitable order. Controller 102 performs these functionsby providing control signals to driver circuitry 104, output stagecircuitry 106, and LC filter circuitry 140, respectively, as describedin additional detail above.

During the calibration mode of operation, transmitter circuitry 100generates a calibration signal and transmits the calibration signal onsignal line 107. Transmitter circuitry 100 generates the calibrationsignal with any suitable frequency for calibrating communications device10. For example, transmitter circuitry 100 may generate the calibrationsignal at a desired channel frequency at a frequency offset by someselected value from a desired channel frequency, or any other suitabledesired frequency such as a frequency that falls within the 3 dB pointfor LC filter circuitry 140 while still maintaining performance.

Controller 102 may provide information to transmitter 100 to select adesired frequency of the calibration signal. In one embodiment,controller 102 receives a user input from user 152 that indicates thedesired frequency of operation of communications device 10. In thisembodiment, controller 102 provides information associated with the userinput to cause transmitter 100 to set the frequency of the calibrationsignal to the desired frequency of operation of the user. In anotherembodiment, controller 102 accesses predefined information regarding afrequency to use for the calibration signal.

Transmitter circuitry 100 generates the calibration signal at a signallevel selected by controller 102. Controller 102 provides controlsignals to driver circuitry 104 and/or output stage circuitry 106 tocause transmitter circuitry 100 to generate the calibration signal at adesignated signal level. Controller 102 selectively receives feedbackfrom level detect circuitry 116 corresponding to the signal levelsgenerated for the RF voltage signal, V_(RF), and the first RF outputvoltage signal, V_(OUT1).

In one embodiment, controller 102 receives a user input from user 152that indicates the desired a signal level of communications device 10.In this embodiment, controller 102 provides information associated withthe user input to driver circuitry 104 and/or output stage circuitry 106to cause transmitter 100 to set the signal level of the calibrationsignal to the desired signal level. In another embodiment, controller102 accesses predefined information regarding a signal level to use forthe calibration signal for one or more frequencies of the calibrationsignal.

Controller 102 adjusts tuning circuitry 114 during the calibration modeto adjust filter response 600 of LC tuning circuitry 140 using controlsignals provided to tuning circuitry 114 so that it tends to maximize orotherwise optimize the strength of the calibration signal on signal line107. In this way, filter response 600 may be adjusted, improved, and/oroptimized to tune the center frequency of LC filter circuitry 140. Inone or more embodiments, controller 102 adjusts the capacitance and/orresistance of tuning circuitry 114 as described above with reference tothe embodiments 114A and 11B of FIGS. 7A and 7B, respectively, tooptimize the strength of the calibration signal on signal line 107. Asnoted above with reference to FIG. 7B, controller 102 may adjust theresistance of tuning circuitry 114 based on the Q filter circuitry 114.Controller 102 selectively receives feedback from level detect circuitry116 corresponding to the first RF output voltage signal, V_(OUT1).Controller 102 may use the feedback to iteratively adjust thecapacitance and/or resistance of tuning circuitry 114 to optimize filterresponse 600 of LC tuning circuitry 140 using any suitable successiveapproximation techniques.

Controller 102 may initiate the calibration mode of operation each timea new channel of communications device 10 is tuned. A new channel may betuned in response to communications device 10 being powered up or reset,user 152 providing a new channel tuning, or controller 102 detecting asignificant change in environmental variables, such as temperature, thatmay affect circuitry in communications device 10. The calibration modeof communications device 10 may occur over a relatively short period oftime such that user 152 may not notice that communications device 10transmits the calibration signal during the calibration mode. Aftercompleting a calibration of communications device 10 in the calibrationsmode, controller 102 may store calibration information for use asstarting points in subsequent calibrations or for error log information.Communications device 10 may begin a normal mode of operation subsequentto the calibration mode using the signal level and tuning settings fortransmitter 100 and tuning circuitry 114, respectively, determinedduring the calibrations mode.

Various algorithms may be implemented to accomplish the calibrationcontemplated by the calibration mode. FIG. 8 is a flow chartillustrating one embodiment of a method for calibrating communicationsdevice 10. The embodiment of the method of FIG. 8 will be described withreference to the embodiment of communications device 10 shown in FIG. 1.

In FIG. 8, controller 102 sets a calibration signal to an initialcalibration frequency as indicated in a block 802. The calibrationfrequency may be set in response to a user input from user 152 or apredefined frequency accessed by or stored in controller 102. Controller102 provides control signals to driver circuitry 104 to sets thecalibration frequency of the calibration signal according to oneembodiment.

Controller 102 sets the calibration signal to an initial calibrationsignal level as indicated in a block 804. The calibration signal levelmay be set in response to a user input from user 152 or a predefinedsignal level accessed by or stored in controller 102. Controller 102provides control signals to driver circuitry 104 and output stagecircuitry 106 to sets the calibration signal level of the calibrationsignal according to one embodiment.

Controller 102 initializes tuning circuitry 114 as indicated in a block806. Controller 102 provides control signals to tuning circuitry 114 toset initial capacitance and/or resistance values of tuning circuitry114. The initial values may be predefined values accessed by or storedin controller 102 or may be values generated by previous calibrationsand stored by controller 102.

Controller 102 detects a signal level of the first RF output voltagesignal, V_(OUT1), of transmitter circuitry 100 as indicated in a block808. Controller 102 activates switch 118B to cause level detectcircuitry 116 to detect the signal level on signal line 107 according toone embodiment. Controller 102 receives information corresponding to thesignal level from level detect circuitry 116 to detect the signal level.

A determination is made by controller 102 as to whether the signal leveldetected in block 808 is out of range as indicated in a block 810. Inone embodiment, controller 102 compares the signal level to a range ofsignal values to make the determination. If the signal level is out ofrange, then controller 102 adjusts the signal level as indicated in ablock 812. Controller 102 adjusts the signal level by providing controlsignals to driver circuitry 104 and/or output stage circuitry 106.

If the signal level is not out of range, then a determination is made bycontroller 102 as to whether a tuning algorithm is complete as indicatedin a block 814. Controller 102 may determine whether the tuningalgorithm is complete by comparing the signal level detected in block808 with any number of previously detected signal levels (i.e., signallevels detected in performing previous iterations of the function ofblock 808) or other predefined information accessible to or stored incontroller 102. In one embodiment, the tuning algorithm may completewhen controller 102 identifies a peak signal response using the signallevels from the iterations of performing the function of block 808. Inother embodiments, the algorithm may complete when other criteria aremet.

If the tuning algorithm is not complete, then controller 102 adjuststuning circuitry 114 as indicated in a block 816. Controller 102 adjuststuning circuitry 114 by providing control signals that cause thecapacitance and/or resistance of tuning circuitry 114 to be increased ordecreased. Controller 102 may iteratively adjust tuning circuitry 114 byrepeatedly performing the function of blocks 814 and 816. For example,controller 102 may perform coarse, medium, and fine tuning of tuningcircuitry 114 by adding or removing high, medium, and low capacitancevalues, respectively, during the iterations.

If the tuning algorithm is complete, then controller 102 sets the signallevel and tuning circuitry settings determined by the algorithm asindicated in a block 818. In particular, controller 102 provides controlsignals to driver circuitry 104 and output stage circuitry 106 to setsthe optimal signal level of the first RF output voltage signal,V_(OUT1), as determined by the algorithm and controller 102 providescontrol signals to tuning circuitry 114 to set the optimal thecapacitance and/or resistance of tuning circuitry 114.

Controller 102 optionally stores the signal level and tuning circuitrysettings in a location that is accessible by or within controller 102 asindicated in a block 820. The stored signal level and tuning circuitrysettings may be accessed by controller 102 for use during subsequentcalibrations.

In addition to the calibration mode just described, controller 102 isconfigured to adjust the signal level of the first RF output voltagesignal, V_(OUT1), on signal line 107 to compensate for properties of anantenna, such as antenna 130, coupled to antenna port 110 or antennaport 112. Controller 102 may receive antenna compensation informationfrom user 152 or may access stored antenna compensation informationassociated with various antennas within communications device 10. Theantenna compensation information may include compensation informationfor any number of frequencies of the first RF output voltage signal.Controller 102 may be configured to interpolate the amount ofcompensation using any suitable linear or non-linear function forvarious frequencies using antenna compensation information provided by auser.

Controller 102 uses the antenna compensation information to set thesignal level of the first RF output voltage signal to desired signalslevels at various frequencies of the first RF output voltage signal.Controller 102 adjusts the signal level by providing control signals todriver circuitry 104 and/or output stage circuitry 106. In embodiment106A of output stage circuitry 106 (FIG. 5), controller 102 adjusts theoutput current, I_(OUT), of adjustable output level circuitry 504 to setthe signal level of the first RF output voltage signal.

FIG. 9 is a table illustrating one embodiment of antenna compensationinformation 900 for use in compensating for parameters of an antenna.Antenna compensation information 900 indicates an amount of compensationto adjust the signal level of the first RF output voltage signal onsignal line 107 for various frequencies. As indicated by antennacompensation information 900, controller 102 increases the signal levelof the first RF output voltage signal by 10% when the frequency of thefirst RF output voltage signal is set to 76 MHz. Similarly, controller102 decreases the signal level of the first RF output voltage signal by10% when the frequency is set to 108 MHz. Controller 102 also increasesthe signal level by 5% when the frequency is set to 84 MHz and decreasesthe signal level by 5% when the frequency is set to 100 MHz. At certainfrequencies, e.g., 92 MHz in the example shown in FIG. 9, controller 102may not provide any compensation for an antenna. Accordingly, controller102 may not adjust the signal level of the first RF output voltagesignal subsequent to the calibration for these frequencies. Controller102 may also interpolate between data points using any suitable functionfor intermediate frequencies, such as 92 MHz in the example of FIG. 9.

FIG. 10 is a block diagram illustrating one embodiment of acommunications device 1000 with receiver circuitry 1002 that shares atleast antenna port 110 with transmitter circuitry 100.

Transmitter circuitry 100 and receiver circuitry 1002 may each use thesame antenna (e.g., antenna 130 on antenna port 110) or may usedifferent antennas (e.g., transmitter circuitry 100 may use an antenna(not shown) on antenna port 112 and receiver circuitry 1002 may useantenna 130 on antenna port 110). Controller 102 operates a switch 1004to selectively connect and disconnect receiver circuitry 1002 fromantenna port 110. In one embodiment, controller 102 connects receivercircuitry 1002 to antenna port 110 in a receive mode of operation anddisconnects receiver circuitry 1002 from antenna port 110 in a transmitmode of operation. In other embodiments, receiver circuitry 1002 is alsocoupled to and shares antenna port 112. In this embodiment, controller102 may operate an additional switch (not shown) to selectively connectand disconnect receiver circuitry 1002 from antenna port 112.

Tuning circuitry 114, level detect circuitry 116, and controller 102 maybe used to calibrate and tune both output signals from the transmitterand input signals received by receiver circuitry 1002 across antennaport 110 using antenna 130. Transmitter circuitry 100 may be used togenerate calibration signals as described above for use in calibratingtuning circuitry 114 for a receive mode of operation such thattransmitter circuitry 100 is turned off subsequent to the calibrationcompleting. If a tuning error occurs as a result of turning offtransmitter circuitry 100 during the receive mode, the error may becompensated for through knowledge of the circuit parameters oftransmitter circuitry 100.

In the embodiment of FIG. 10, each antenna port 110 and 112 forms ainput/output pad in integrated communications device 1000 that includesa conductor configured to couple to an antenna or other circuitry thatis external to communications device 1000. The input/output pads may becoupled to electrostatic discharge (ESD) protection circuitry (notshown) or other input or output buffer circuitry (not shown) incommunications device 1000. In the embodiment shown in FIG. 10, anantenna 130 and an inductor 132 connect to antenna port 110. In otherembodiments, antenna 130 and inductor 132 are omitted and anotherantenna (not shown) connects to antenna port 112. In furtherembodiments, inductor 132 may omitted, may be located integrated on-chipwith communications device 1000, or may be included with antenna 130.

FIG. 11 is a block diagram illustrating one embodiment of a portablecommunications system 1100 that includes communications device 10 asshown in FIG. 1 or communications device 1000 as shown in FIG. 10.Portable communications system 1100 may be any type of portable ormobile communications device such as a mobile or cellular telephone, apersonal digital assistant (PDA), an audio and/or video player (e.g., anMP3 or DVD player), a wireless telephone, and a notebook or laptopcomputer. Portable communications system 1100 includes communicationsdevice 10 (FIG. 1) or 1000 (FIG. 10), an input/output system 1102, apower supply 1104, and an antenna 1106 among other components. Antenna1106 may couple to either antenna port 110 or antenna port 112 ofportable communications device 10/1000 of portable communications system1100.

Input/output system 1102 receives information from a user and providesthe information to communications device 10 or 1000. Input/output system1102 also receives information from mobile communications device 10 or1000 and provides the information to a user. The information may includevoice and/or data communications, audio, video, image, or othergraphical information. Input/output system 1102 includes any number andtypes of input and/or output devices to allow a user provide informationto and receive information from portable communications system 1100.Examples of input and output devices include a microphone, a speaker, akeypad, a pointing or selecting device, and a display device.

Power supply 1104 provides power to portable communications system 1100,input/output system 1102, and antenna 1106. Power supply 1104 includesany suitable portable or non-portable power supply such as a battery oran AC plug.

In embodiments that include communications device 10, communicationsdevice 10 communicates with a receiver 1110 or one or more remotelylocated hosts (not shown) in radio frequencies using antenna 1106.Communications device 1000 transmits information to receiver 1110 or oneor more remotely located hosts in radio frequencies using antenna 1106as indicated by a signal 1120. In other embodiments, communicationsdevice 1000 communicates with receiver 1110 or one or more remotelylocated hosts using other frequency bands.

In embodiments that include communications device 1000, communicationsdevice 1000 communicates with receiver 1110 or other remotely locatedhosts in radio frequencies using antenna 1106. Communications device1000 transmits information to receiver 1110 or other remotely locatedhosts in radio frequencies using antenna 1106 as indicated by a signal1120. Communications device 1000 receives information from receiver 1110or other remotely located hosts in radio frequencies using antenna 1106as indicated by a signal 1130. In other embodiments, communicationsdevice 1000 communicates with receiver 1110 or one or more remotelylocated hosts using other frequency bands.

In the above embodiments, a variety of circuit and process technologiesand materials may be used to implement the communications systemsaccording to the invention. Examples of such technologies include metaloxide semiconductor (MOS), p-type MOS (PMOS), n-type MOS (NMOS),complementary MOS (CMOS), silicon-germanium (SiGe), gallium-arsenide(GaAs), silicon-on-insulator (SOI), bipolar junction transistors (BJTs),and a combination of BJTs and CMOS (BiCMOS).

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A communications device comprising: an antenna port configured forcoupling to any given one of multiple different antennas; transmittercircuitry configured to broadcast a radio frequency (RF) output signalacross any given one of the multiple different antennas that is coupledto the antenna port at a first frequency; stored antenna compensationinformation corresponding to each given one of the multiple differentantennas that indicates an amount of amplitude compensation to applydepending on which given one of the multiple antennas is coupled to theantenna port in order to adjust the corresponding amplitude level atwhich the RF output signal is broadcast at the first frequency across agiven one of the multiple antennas when it is coupled to the antennaport, the amplitude compensation indicated by the stored antennacompensation information being different at the first frequency for eachof the multiple different antennas; and a controller configured toadjust an amplitude level at which the RF output signal is broadcast atthe first frequency across a first one of the multiple antennas when itis coupled to the antenna port by the amount indicated by the storedantenna compensation information corresponding to the first antenna forthe first frequency so as to set the amplitude of the RF output signalto a first amplitude level at which the RF output signal is broadcast atthe first frequency across the first antenna coupled to the antennaport, based on the antenna compensation information; wherein the antennacompensation information is configured to compensate for properties ofeach given one of the multiple antennas when it is coupled to theantenna port while the RF output signal is being broadcast at the firstfrequency, and wherein the antenna port, the transmitter circuitry, andthe controller are at least partially integrated on the same integratedcircuit.
 2. The communications device of claim 1 wherein the controlleris configured to access the antenna compensation information within thecommunications device, the antenna compensation information being storedinformation that indicates an amount of amplitude compensation to applyat each of multiple different frequencies depending on which given oneof the multiple antennas is coupled to the antenna port in order toadjust the corresponding amplitude level at which the RF output signalis broadcast across a given one of the multiple antennas when it iscoupled to the antenna port.
 3. The communications device of claim 1wherein the controller is configured to receive a selection of theantenna compensation information from a user.
 4. The communicationsdevice of claim 1 wherein the controller is configured to increase theamplitude level at which the RF output signal is broadcast across thefirst antenna for the first frequency of the RF output signal based onthe stored antenna compensation information, and wherein the controlleris configured to decrease the amplitude level at which the RF outputsignal is broadcast across the first antenna for a second frequency ofthe RF output signal that differs from the first frequency based on thestored antenna compensation information.
 5. The communications device ofclaim 1 where the antenna compensation information comprises at leastone stored table of different amplitude level adjustment amountscorresponding to different respective frequencies at which the RF outputsignal is broadcast across multiple different antennas, the amplitudecompensation indicated by the stored antenna compensation informationbeing different for each of the multiple different antennas.
 6. Thecommunications device of claim 1, wherein the stored antennacompensation information further indicates an amount of amplitudecompensation to apply at each of multiple different frequencies for eachgiven one of the multiple different antennas, the amount of amplitudecompensation being different for each of the multiple differentfrequencies for each of the multiple different antennas; and wherein thecontroller is further configured to adjust an amplitude level at whichthe RF output signal is broadcast at each of the multiple differentfrequencies across a given one of the multiple antennas when it iscoupled to the antenna port by the amount indicated by the storedantenna compensation information corresponding to the given antennacoupled to the antenna port based on the current selected frequency soas to set the amplitude of the RF output signal to a current amplitudelevel at which the RF output signal is broadcast at the current selectedfrequency across the given antenna coupled to the antenna port based onthe antenna compensation information.
 7. The communications device ofclaim 1, wherein the controller is further configured to adjust theamplitude level at which the RF output signal is broadcast at the firstfrequency across a first one of the multiple antennas when it is coupledto the antenna port by the amount indicated by the stored antennacompensation information corresponding to the first antenna for thefirst frequency so as to change the amplitude of the RF output signalfrom a first amplitude level at which the RF output signal is broadcastat the first frequency across the first antenna to a second anddifferent amplitude level at which the RF output signal is broadcast atthe first frequency across the same antenna coupled to the same antennaport, the RF output signal remaining at the first frequency in responseto the amplitude level being adjusted by the amount indicated by theantenna compensation information.
 8. The communications device of claim1 wherein the controller is configured to adjust the amplitude level atwhich the RF output signal is broadcast across the first antennasubsequent to completing a calibration mode of operation.
 9. Thecommunications device of claim 8 wherein the controller is configured toadjust tuning circuitry coupled to the antenna port during thecalibration mode of operation.
 10. The communications device of claim 1wherein the transmitter includes output stage circuitry configured togenerate the RF output signal using an intermediate signal, and whereinthe controller is configured to adjust the amplitude level at which theRF output signal is broadcast across the first antenna by providing afirst control signal to the output stage circuitry.
 11. Thecommunications device of claim 10 wherein the output stage circuitryincludes adjustable level circuitry coupled to a transconductanceamplifier and configured to receive the control signal.
 12. Thecommunications device of claim 10 wherein the transmitter includesdriver circuitry configured to generate the intermediate signal andprovide the intermediate signal to the output stage circuitry, andwherein the controller is configured to adjust a signal level of theintermediate signal by providing a second control signal to the drivercircuitry.
 13. The communications device of claim 1 wherein thecontroller is configured to increase the amplitude level to first levelat which the RF output signal is broadcast across a first antenna forthe first frequency of the RF output signal based on the stored antennacompensation information when the first antenna is coupled to theantenna port; and wherein the controller is configured to decrease theamplitude level to a second and lower level at which the RF outputsignal is broadcast across a second and different antenna for the firstfrequency of the RF output signal based on the stored antennacompensation information when the second antenna is coupled to theantenna port.
 14. The communications device of claim 13 wherein thefirst antenna has a higher impedance than the second antenna.
 15. Amethod performed by a controller in a communication device withtransmitter circuitry, the method comprising: accessing stored antennacompensation information corresponding to multiple different antennasthat indicates an amount of amplitude compensation to apply depending onwhich given one of the multiple antennas is coupled to an antenna portof the communications device while a radio frequency (RF) output signalof a first frequency is being broadcast across the given one of themultiple antennas coupled to the antenna port, the amplitudecompensation indicated by the stored antenna compensation informationbeing different at the first frequency for each of the multipledifferent antennas; and compensating for properties of the given antennacoupled to the antenna port while the RF output signal is beingbroadcast at the first frequency across the given antenna by adjustingan amplitude level of the RF output signal generated by the transmittercircuitry at the first frequency and broadcast across the given antennaby an amount indicated by the antenna compensation information for thefirst frequency so as to set the amplitude of the RF output signal to afirst amplitude level at which the RF output signal is broadcast at thefirst frequency across the given antenna based on the antennacompensation information.
 16. The method of claim 15 further comprising:adjusting the amplitude level of the RF output signal by increasing theamplitude level.
 17. The method of claim 15 further comprising:adjusting the amplitude level of the RF output signal by decreasing theamplitude level.
 18. The method of claim 15 further comprising:accessing the antenna compensation information within the communicationsdevice, the antenna compensation information being stored informationthat indicates an amount of amplitude compensation to apply at each ofmultiple different frequencies depending on which given one of themultiple antennas is coupled to the antenna port in order to adjust thecorresponding amplitude level at which the RF output signal is broadcastacross a given one of the multiple antennas when it is coupled to theantenna port.
 19. The method of claim 15 further comprising: receiving aselection of the antenna compensation information from a user.
 20. Themethod of claim 15 further comprising: adjusting the amplitude level ofthe RF output signal subsequent to completing a calibration mode ofoperation.
 21. The method of claim 15 where the antenna compensationinformation comprises at least one stored table of different amplitudelevel adjustment amounts corresponding to different respectivefrequencies at which the RF output signal is broadcast across multipledifferent antennas, the amplitude compensation indicated by the storedantenna compensation information being different for each of themultiple different antennas.
 22. The method of claim 15, wherein thestored antenna compensation information further indicates an amount ofamplitude compensation to apply at each of multiple differentfrequencies for each given one of the multiple different antennas, theamount of amplitude compensation being different for each of themultiple different frequencies for each of the multiple differentantennas; and where the method further comprises compensating forproperties of the given antenna coupled to the antenna port while the RFoutput signal is being broadcast at a current selected one of themultiple different frequencies by adjusting an amplitude level of the RFoutput signal generated by the transmitter circuitry at the givenfrequency and broadcast across the given antenna when it is coupled tothe antenna port by the amount indicated by the stored antennacompensation information corresponding to the given antenna coupled tothe antenna port based on the current selected frequency so as to setthe amplitude of the RF output signal to a current amplitude level atwhich the RF output signal is broadcast at the current selectedfrequency across the given antenna coupled to the antenna port based onthe antenna compensation information.
 23. The method of claim 15 furthercomprising: accessing the stored antenna compensation information foruse in compensating for properties of the given one of the multipleantennas coupled to the antenna port of the communications device whilea radio frequency (RF) output signal of the first frequency is beingbroadcast at different amplitude levels across the same given one of themultiple antennas coupled to the same antenna port; and compensating forproperties of the given antenna coupled to the antenna port while the RFoutput signal is being broadcast at the first frequency at differentamplitude levels across the same given antenna by adjusting an amplitudelevel of the RF output signal generated by the transmitter circuitry atthe first frequency and broadcast across the given antenna by an amountindicated by the antenna compensation information for the firstfrequency so as to change the amplitude of the RF output signal from afirst amplitude level at which the RF output signal is broadcast at thefirst frequency across the given antenna to a second and differentamplitude level at which the RF output signal is broadcast across thesame given antenna coupled to the same antenna port, the RF outputsignal remaining at the frequency in response to the amplitude levelbeing adjusted by the amount indicated by the antenna compensationinformation.
 24. The method of claim 15 further comprising increasingthe amplitude level to a first level at which the RF output signal isbroadcast across a first antenna for the first frequency of the RFoutput signal based on the stored antenna compensation information whenthe first antenna is coupled to the antenna port; and decreasing theamplitude level to a second and lower level at which the RF outputsignal is broadcast across a second and different antenna for the firstfrequency of the RF output signal based on the stored antennacompensation information when the second antenna is coupled to theantenna port.
 25. The method of claim 24 wherein the first antenna has ahigher impedance than the second antenna.
 26. A communication devicecomprising: an antenna port coupled to a first antenna; transmittercircuitry including adjustable level circuitry and configured tobroadcast a radio frequency (RF) output signal across the first antennaat a first frequency; stored antenna compensation informationcorresponding to each given one of multiple different antennas thatindicates an amount of amplitude compensation to apply depending onwhich given one of the multiple antennas is coupled to the antenna portin order to adjust the corresponding amplitude level at which the RFoutput signal is broadcast at the first frequency across a given one ofthe multiple antennas when it is coupled to the antenna port, theamplitude compensation indicated by the stored antenna compensationinformation being different at the first frequency for each of themultiple different antennas; and a controller configured to provide afirst control signal to the adjustable level circuitry to cause anamplitude level at which the RF output signal is broadcast at the firstfrequency across the first antenna coupled to the antenna port to beadjusted by the amount indicated by the stored antenna compensationinformation corresponding to the first antenna for the first frequencyso as to set the amplitude of the RF output signal to a first broadcastamplitude level at which the RF output signal is broadcast at the firstfrequency across the first antenna based on the antenna compensationinformation; wherein the antenna compensation information is configuredto compensate for properties of each given one of the multiple antennaswhen it is coupled to the antenna port while the RF output signal isbeing broadcast at the first frequency and wherein the antenna port, thetransmitter circuitry, and the controller are at least partiallyintegrated on the same integrated circuit.
 27. The communications deviceof claim 26 wherein the transmitter circuitry includes atransconductance amplifier, and wherein the adjustable level circuitryis coupled to the transconductance amplifier and is configured toreceive the first control signal.
 28. The communications device of claim27 wherein the transmitter circuitry includes driver circuitryconfigured to generate an intermediate signal and provide theintermediate signal to the transconductance amplifier, and whereincontroller is configured to provide a second control signal to thedriver circuitry to cause the signal level of the intermediate signal tobe adjusted.
 29. The communications device of claim 28 wherein thedriver circuitry includes RF conditioning circuitry, and wherein the RFconditioning circuitry is configured to receive the second controlsignal.
 30. A communications system comprising: a first antenna; acommunications device including: an antenna port coupled to the firstantenna; transmitter circuitry configured to broadcast a radio frequency(RF) output signal across the first antenna coupled to the antenna portat a first frequency; stored antenna compensation informationcorresponding to each given one of multiple different antennas thatindicates an amount of amplitude compensation to apply depending onwhich given one of the multiple antennas is coupled to the antenna portin order to adjust the corresponding amplitude level at which the RFoutput signal is broadcast at the first frequency across a given one ofthe multiple antennas when it is coupled to the antenna port, theamplitude compensation indicated by the stored antenna compensationinformation being different at the first frequency for each of themultiple different antennas; and a controller configured to adjust anamplitude level at which the RF output signal is broadcast at the firstfrequency across the first antenna coupled to the antenna port by theamount indicated by the stored antenna compensation informationcorresponding to the first antenna for the first frequency so as to setthe amplitude of the RF output signal from a first amplitude level atwhich the RF output signal is broadcast at the first frequency acrossthe first antenna based on the antenna compensation information; whereinthe antenna compensation information is configured to compensate forproperties of each given one of the multiple antennas when it is coupledto the antenna port while the RF output signal is being broadcast at thefirst frequency and wherein the antenna port, the transmitter circuitry,and the controller are at least partially integrated on the sameintegrated circuit; and an input/output system configured to communicatewith the communications device.
 31. The communications system of claim30 wherein the controller is configured to access the antennacompensation information within the communications device, the antennacompensation information being stored information that indicates anamount of amplitude compensation to apply at each of multiple differentfrequencies depending on which given one of the multiple antennas iscoupled to the antenna port in order to adjust the correspondingamplitude level at which the RF output signal is broadcast across agiven one of the multiple antennas when it is coupled to the antennaport.
 32. The communications system of claim 30 wherein thecommunications device is configured to receive a selection of theantenna compensation information from a user.
 33. The communicationssystem of claim 30 where the antenna compensation information comprisesat least one stored table of different amplitude level adjustmentamounts corresponding to different respective frequencies at which theRF output signal is broadcast across multiple different antennas, theamplitude compensation indicated by the stored antenna compensationinformation being different for each of the multiple different antennas.